The present application relates to a semiconductor structure and a method of forming the same. More particularly, the present application relates to a FinFET having an asymmetric threshold voltage distribution which is provided by partially modifying the channel material that is nearest to the drain side using an epitaxial growth process.
The lateral asymmetric channel (LAC) doping profile approach provides one of the most effective ways to improve the electrical characteristics of field effect transistors (FETs). For LAC devices, the doping concentration of the source side is higher than that of the drain side in the channel region. The channel potential transition at the source side channel region is much stepper than that of the other channel regions, while the device is operating due to non-uniform channel doping. Such a steep potential distribution near the source side enhances the lateral channel electric field and this increases the carrier mobility.
The LAC doping approach, however, suffers from channel dopant diffusion and dopant variation. Also, it is difficult to design short channel devices using the LAC doping approach. As such, there is a need for providing a semiconductor structure having an asymmetric threshold voltage distribution that is formed without using the LAC doping approach.